1. Field
The embodiments discussed herein are related to an allocation control program embodied in a computer-readable medium for dispersedly arranging logical volumes in a plurality of storage apparatuses, and an allocation control apparatus and an allocation control method therefor.
2. Description of the Related Art
Up to now, a dispersion-type multi-node storage system has been proposed in which a plurality of storage apparatuses are dispersedly arranged on a network to function in cooperation for improving a performance and a reliability of the system. In the multi-node storage system, a virtual logical volume in accordance with a request from a client is generated. This logical volume is divided into predetermined divided areas to be allocated to physical storage areas of a plurality of storage apparatuses. At this time, management information having the divided area of the logical volume associated with the physical storage area allocated is stored in the storage apparatus together with data. On the basis of this management information, an access processing to the physical storage area is performed.
In such a multi storage system, for an operational convenience or the like, a case may occur in which the logical volume in operation is duplicated to create a duplicate logical volume. In a creation processing for the duplicate logical volume in the related art, first, a physical storage area of the storage apparatus is allocated while corresponding to the duplicate logical volume. Then, data of the logical volume at a duplication source is copied in the physical storage area of the storage apparatus allocated to the duplicate logical volume.
A method is proposed with which at the time of the copy processing, a link is set for the duplicate logical volume where the allocation is performed and the logical volume at the duplication source, and the data is copied on the basis of the link. For example, see Japanese Laid-open Patent Publication No. 2007-122463. This link is cut off after the end of the duplication.
Also, a method is proposed with which as to a duplication of a logical disk composed of a disk and a magnetic tape, a physical data copy on the tape is not performed, and only management information is copied to create another logical volume. For example, see Japanese Laid-open Patent Publication No. 2007-323589. According to this method, virtual logical volumes at the copy source and the copy destination share the physical storage area.
However, a problem occurs that the physical storage area of the duplication processing for allocating the logical volume and copying all the data of the logical volume at the duplication source takes much time for the copy. Also, in an area where the data of the duplicate logical volume is not updated, the same data is set for the logical volume at the duplication source and the logical volume at the duplication destination, which is also redundant.
On the other hand, a method of copying only the management information at the time of the duplication of the logical volume in the related art is difficult to be applied to a multi-node system where a plurality of computers function in cooperation to manage the physical storage area. In the multi-node storage system, as described above, the access processing is performed on the basis of the management information in which the physical storage areas dispersedly arranged in the respective storage apparatuses are associated with the divided areas of the logical volume. That is, on the basis of the management information, the physical storage area corresponding to an address of the logical volume where an access request occurs is identified to perform the access processing. For this reason, in a case where the access request destination is the duplicate logical volume, the duplicate data needs to be stored in the allocated physical storage area, and it is necessary to previously perform the copy processing to the duplicate logical volume described above.
In a case where the logical volume at the duplication source and the duplicate logical volume share the physical storage area, the physical storage area allocated to the logical volume at the duplication source needs to be set in the management information of the duplicate logical volume. However, this allocation is appropriately updated by the control apparatus, and the management information is also changed in accordance to this. As it is necessary to perform a complex processing in order to keep an up-to-date state of the management information stored in the storage apparatus, it is not simple for the duplicate logical volume and the logical volume at the duplication source to share the physical storage area.
In view of the above-mentioned circumstances and existing problems, it is an object to provide an allocation control program with which a creation time for a duplicate logical volume at a time of a duplication of a logical volume is shortened and also a utilization efficiency of a physical storage area is increased, an allocation control apparatus, and an allocation control method of implementing same.